Back in college, in 1996 (I believe) I frequently played the pre-release version of SubSpace, a massively multiplayer online game that was originally designed as a project to test the affects of lag over a modem. If I recall correctly, I first played using a 14.4k baud modem... and it worked. Here's a recent screen shot, Christmas themed because it's that time of the year:
Fast forward ten years, and despite being a 10-year old 2D game, the original company abandoning it, and enthusiests re-writing the client from scratch (!), it still has a fairly strong following. Sure, the graphics have been surpassed by 3D engines long ago, but as a top-down 2D game, they look as good as you could expect given the format, and at 1600x1200 I have no complaints.
To add to that, the problem great thing about SubSpace Continuum is that it not only has high replay value, but the controls are also designed in such a way that you can play the game and chat without switching modes or doing anything awkward. I don't play very often and I barely chat at all anymore, but it's still an ingenious and very natural system. I'm considering suggesting that future meetings between groups within IE take place in private zones using Continuum so that I am in a better position to annialate those who disagree with me. ;-)
One amusing thing is that even though I've joined and re-joined using different names over the years (I play for a few months and stop for a couple years), I still recognize some players from back when I originally played ten years ago. And yes, they are the same people; it's not a coincidence.
My only regret is that I never purchased a copy of SubSpace (although I didn't pirate it either; I just didn't play during the period it required a retail copy). This is one great game, and the developers deserved to be compensated appropriately.
Edit: I suppose I should give a link so that people can download and play SubSpace/Continuum: http://www.subspacedownloads.com, since it's free afterall.
Edit2 (sorry): The reason I added "Real-time" to the title is that I don't want to compare this to Tradewars, Yankee Trader, or any of the old BBS games quite yet. :-)